Effect of Use of Entropy Monitoring on Consumption of Sevoflurane Inhalational Agent in Patients Undergoing Off-Pump Coronary Artery Bypass Graft Surgery: A Randomized, Double Blinded, Controlled Study

Monitoring the depth of Anesthesia using Entropy modality is essential and resourceful as it allows for more accurate hypnotic drug administration and decreased anesthetic drug consumption and shortens the recovery time. This study was performed to evaluate the effect of entropy monitoring on Sevoflurane consumption in patients undergoing Off Pump Coronary Artery Bypass Graft Surgery.

A total of 60 patients of ages between 40 – 70 years and of either sex with American Society of Anesthesiologist (ASA) grade 2 and 3, planned for Off Pump Coronary Artery Bypass Graft Surgery were randomly allocated to two groups in this Randomized Controlled Trial. In the control group i.e. Group B, Sevoflurane was titrated according to changes in clinical parameters (Heart Rate (HR) and Blood Pressure (BP) changes within 20% of baseline values) and in the study group i.e. Group A, Sevoflurane was titrated to maintain State Entropy (SE) values between 40-60 accordingly. Response Entropy (RE) and State Entropy (SE) values were continuously recorded in both the groups but were displayed on the monitor only in the study group and were not displayed to the anesthesiologist in the control group. The entropy values, Sevoflurane Consumption and recovery times were compared amongst the two groups. Patients in both the groups were ventilated on Volume Control Mode of ventilator with 100% oxygen @ 2L/min.

There were no significant results in terms of age, sex, ASA Grade and NYHA Grade amongst the two groups. Sevoflurane consumption and time of recovery were significantly reduced in the study group i.e. Group A than the Control group i.e. Group B (p value <0.001; Sevoflurane consumption: 7.03±0.67 ml/hr vs 12.42±0.68 ml/hr; Recovery Time 6.47±0.65 hr vs 12.05±1.11 hr). Response and State Entropy values were lower in the control group than the study group (p < 0.001) during the maintenance phase of anesthesia. Systolic Blood Pressure values during skin incision, sternotomy and at the time of completion of all grafts were significantly lower in study group as compared to the control group.

Monitoring the Depth of Anesthesia using Entropy Monitoring leads to significant reduction in Sevoflurane consumption and significant faster recovery rate from surgery.